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Science 24 July 1992:
Vol. 257. no. 5069, pp. 511 - 514
DOI: 10.1126/science.257.5069.511
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Articles

Existence of an Orientational Electric Dipolar Response in C60 Single Crystals

G. B. Alers 1, Brage Golding 1, A. R. Kortan 2, R. C. Haddon 2, and F. A. Theil 2

1 Department of Physics and Astronomy and the Center for Fundamental Materials Research, Michigan State University, East Lansing, MI 48824
2 AT&T Bell Laboratories, Murray Hill, NJ 07974

The dielectric constant isin and conductivity sgr of undoped C60 single crystals have been measured as a function of temperature, 10 K < T < 330 K, and frequency, 0.2 kilohertz < f < 100 kilohertz. On cooling below the first-order structural phase transition at 260 K, a Debye-like relaxational contribution to the dielectric response is observed, which requires the presence of permanent electric dipoles. The relaxation rate is thermally activated with a broad distribution of energies centered at 270 millielectron volts. The existence of a dipole moment in C60 is unexpected, because it is precluded by symmetry for the pure ordered cubic phase. These data suggest that the high degree of frozen-in orientational disorder of the C60 molecules is responsible for the existence of electric dipolar activity.

Submitted on April 28, 1992
Accepted on May 28, 1992


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Magnetic Susceptibility of Molecular Carbon: Nanotubes and Fullerite.
A. P. Ramirez, R. C. Haddon, O. Zhou, R. M. Fleming, J. Zhang, S. M. McClure, and R. E. Smalley (1994)
Science 265, 84-86
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Science. ISSN 0036-8075 (print), 1095-9203 (online)